Along with the rapid development and availability of portable electronic products, lithium ion secondary batteries, due to their properties, including light in weight, high voltage, and high energy density, etc., have ever increasing demands in the modern era. Furthermore, the use of polymer electrolytes in the lithium ion secondary batteries has become more and more important and attracted wide attention in research for size reduction and increasing flexibility of the electronic products.
The advantages of using a polymer electrolyte in a lithium ion polymer battery include: free of the risk of leakage of electrolyte, capable of being used to produce a battery with an ultra-thin and large area or with an angle, light in weight, lower vapor pressure and lower auto-discharge rate. These advantages greatly increase the commercial applications of lithium ion secondary batteries.
In order to develop thin type batteries with a flexible and thin shell, there are currently a plurality of gel polymer materials, together with electrolyte compositions, under investigation and study. These gel polymer materials include poly(ethylene oxide) (PEO), poly(methyl methacrylate) (PMMA), Poly(vinylidene fluoride) (PVDF), polyacrylonitrile (PAN), and derivatives or co-polymers thereof. An ordinary process of producing a gel polymer electrolyte for a polymer battery comprises forming a film from the gel polymer electrolyte; removing the solvent from the film; mounting the polymer film between two layers of an active material and stacking the resulting composite or coating the polymer film on the surface of an active material to form a battery core; and injecting a liquid electrolyte into the battery shell and binding the electrode plates. Thus, the laminated structure of electrode plates will have reduced expansion or shrinkage during the association/dissociation of lithium ions in the course of the charge/discharge process. As a result, the batteries produced have a long operation lifespan. However, such a production process is complex.